(1) Field of the Invention
The present invention relates to an adjustment apparatus for cancelling discrepancy between the optical axis of an optical lens and the optical axis of an optical system in a TV camera.
(2) Description of the Related Art
In a TV camera, an optical image put in from an optical lens fixed and supported on a lens mount is resolved, in case of a color image, into optical image signals of the three primary colors R (red), G (green) and B(blue) through an optical system (a prism and the like), and these optical image signals are converted to electric optical signals by an image pickup element such as CCD or an image pickup tube and after various processings, video signals are put out from the image pickup element.
In a TV camera of this type, it is necessary that the optical axes of the optical lens, optical system and pickup element should be in agreement with one another at a high precision. The optical system and image pickup element are integrally assembled, for example, by bonding and fixing CCD to a prism, and the axes of the optical system and pickup element can easily be made in agreement with each other. However, even though the center O of the image pickup face is in agreement with the optical axis of the optical system, when discrepancy .DELTA.t is produced between this optical axis and the optical axis O' of the optical lens at zoom-up photographing, if photographing is carried out at x magnifications in this state, the image shifts from the center O of the image pickup face toward the optical axis O' by .DELTA.t.multidot.(x-1)/x.
This shift becomes a considerably large discrepancy when seen on a monitor picture, and it sometimes happens that the portion to be picked up protrudes from the picture.
In the case where an image pickup tube is used as the image pickup element, the above-mentioned discrepancy of the optical axis can easily be cancelled by magnetically deflecting and regulating optical beams. However, in the case where a solid image pickup element developed recently as an image pickup element for the miniaturization is used, the discrepancy of the optical axis cannot be cancelled and therefore, the discrepancy of the optical axis is a serious problem. Even in case of a TV camera comprising an image pickup tube as the image pickup element, nothing is better than omission of deflection and regulation of beams.
In view of the foregoing, it is necessary that the discrepancy of the optical axis between the optical lens and the optical system should be minimized. According to the conventional technique, the dimensions are strictly controlled by using a special tool at the assembling, or the precisions of parts are increased. However, even if the discrepancy is small at the assembling, backlashes of respective parts increase with the lapse of time, resulting in increase of the discrepancy, or the discrepancy is increased by exchange of lenses.
In order to regulate the thus produced discrepancy of the optical axis, there cannot but be adopted a method in which the camera is disassembled, the optical axis is regulated and the camera is assembled again.